The Suffolk Argus
Butterfly Conservation’s International Symposium ‘The 2010 Target and Beyond for Lepidoptera’ was the theme for the 6th International Symposium held at Reading University, during the 26th-28th March 2010. Welcomed by an inspiring speech from Sir David Attenborough, 250 delegates from Britain, continental Europe, America, Africa and Japan attended lectures on subjects that ranged across topics such as ‘British Butterfly Distribution and the 2010 Target’, ‘How are Butterflies Doing in Europe?’, ‘Countryside Moth Conservation’ and ‘Butterfly Response to Climate Change’.
“suitable sites”, and the difference is often not readily apparent to the human eye. Adonis Blue often prefers to lay in short sward in preference to “perfect looking” adjacent patches loaded with nectar and larval host plants. Sites with general diversity and high species counts also have high numbers (butterflies/acre).
Rob Parker shares some of his gleanings from the Symposium
Abandonment leads to scrub encroachment and progressive loss of diversity. This can be measured at suitable sites (an Estonian island was assessed) and floral & faunal degradation was quite rapid. Declines in butterfly populations were noticeable before floral decline was detected. Abandonment is occurring across Eastern Europe as smalltime farmers give up and move to towns. In some ways, planting of trees in former grassland in UK as “conservation areas” can amount to abandonment of grassland habitat.
Larval Habitat Needs Various speakers drew attention to very precise needs for successful completion of the larval stage. Egg-laying criteria were very precise, and larval survival depended on a variety of factors. Optimal habitat was needed particularly at the margins of range. Some factors: niche microclimate, aspect, shelter, soil type, drainage, sun or shade, sward height, temperature (optima differ for species), quantity of larval host plant(s), quality of larval host plant’s growth & situation (sprawling over rocks, climbing up other vegetation), predation by host-specific parasites, casual grazing, management.
The decline of nectar sources is a general phenomenon driven by eutrophication and has a direct impact on bee and butterfly abundance. Actually, the rate of nitrogen deposition has been reduced over the past decade, but the effects are presumably cumulative.
Site Quality Site size was considered less important than site diversity. Sites with optimum habitat often have the carrying capacity to support populations a hundred times as great as
Extinction Debt Progressive degradation has inertia, and
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